System and method for carrier aggregation for wireless local area networks

ABSTRACT

Embodiments are provided herein for improving carrier aggregation for wireless networks. A plurality of bandwidth channels are assigned to a basic service set (BSS) for transmissions. Specifically, the bandwidth channels are divided into multiple channel segments corresponding to multiple primary or alternate primary channels. A channel segment possibly further includes one or more additional secondary channels. The locations of the primary or alternate primary channels that correspond to the channel segments of the BSS are then broadcasted in the network. When a station or AP receives this BSS information, it searches for an available primary or alternate primary channel of the BSS to begin transmission. Upon detecting an available primary channel or alternate primary channel that is not used for another transmission, the station or AP transmits data on the channel segment corresponding to the detected primary or alternate primary channel.

This application is a continuation of U.S. Non-Provisional patentapplication Ser. No. 14/061,464 filed on Oct. 23, 2013 and entitled“System and Method for Carrier Aggregation for Wireless Local AreaNetworks,” which claims the benefit of U.S. Provisional Application No.61/717,919 filed on Oct. 24, 2012 and entitled “System and Method forWLAN Generalized Carrier Aggregation,” both of which are herebyincorporated herein by reference as if reproduced in their entireties.

TECHNICAL FIELD

The present invention relates to the field of wireless networkcommunications, and, in particular embodiments, to a system and methodfor carrier aggregation for wireless local area networks.

BACKGROUND

Achieving higher data rates generally is a goal of any network design.According to communication theory, the achieved data rate (e.g.,measured in megabits per second (bps)) of any physical (PHY) layerdesign is proportional to the channel bandwidth (e.g., measured inmegahertz (Hz)). Wider channels generally can sustain higher data ratescompared to narrow channels. In many networking scenarios, only channelsof narrow bandwidth are available, for instance either due to regulationor spectrum availability. In these cases a wider channel can beconstructed by grouping together or aggregating a number of narrowchannels to form a wider channel. The technique by which this groupingis achieved is referred to as carrier aggregation. However, currentcarrier aggregation technique for wireless local area networks (WLANs)can waste bandwidth resource when assigning larger aggregated bandwidthto legacy systems that are not capable of using the entire aggregatedbandwidth range. There is a need for an improved carrier aggregationscheme that handles such situations.

SUMMARY OF THE INVENTION

In accordance with an embodiment, a method implemented by a networkcomponent for carrier aggregation for wireless networks includesassigning, to a basic service set (BSS) comprising a plurality ofstations and an access point of the wireless network, a plurality ofbandwidth channels for transmissions. The method further includesdividing the bandwidth channels into multiple channel segmentscorresponding to multiple prime channels in the bandwidth channels. Thelocations of the prime channels for the channel segments of the BSS arethen broadcasted in the network.

In accordance with another embodiment, a method implemented by acommunication device for supporting carrier aggregation in a wirelessnetwork includes receiving BSS information indicating a plurality ofprime channels for a BSS. The prime channels correspond to a pluralityof channel segments of the BSS. The method further includes, upondetermining to start a transmission, searching for an available andunused prime channel of the BSS. Upon detecting an available and unusedprime channel of the BSS, a frame is transmitted on the channel segmentcorresponding to the detected prime channel.

In accordance with another embodiment, a network component for carrieraggregation for wireless networks includes at least one processor and anon-transitory computer readable storage medium storing programming forexecution by the at least one processor. The programming includinginstructions to assign, to a BSS comprising a plurality of stations andan access point of the wireless network, a plurality of bandwidthchannels for transmissions. The bandwidth channels are divided intomultiple channel segments corresponding to multiple prime channels inthe bandwidth channels. The programming further includes instructions tobroadcasting, in the network, locations of the prime channels for thechannel segments of the BSS.

In accordance with yet another embodiment, a communication devicesupporting carrier aggregation in a wireless network includes at leastone processor and a non-transitory computer readable storage mediumstoring programming for execution by the at least one processor. Theprogramming includes instructions to receive BSS information indicatinga plurality of prime channels of a BSS. The prime channels correspond toa plurality of channel segments of the BSS. The programming includesfurther instructions to, upon determining to start a transmission,search for an available and unused prime channel of the BSS, and upondetecting an available and unused prime channel of the BSS, transmit aframe on the channel segment correspond to the detected prime channel.

The foregoing has outlined rather broadly the features of an embodimentof the present invention in order that the detailed description of theinvention that follows may be better understood. Additional features andadvantages of embodiments of the invention will be describedhereinafter, which form the subject of the claims of the invention. Itshould be appreciated by those skilled in the art that the conceptionand specific embodiments disclosed may be readily utilized as a basisfor modifying or designing other structures or processes for carryingout the same purposes of the present invention. It should also berealized by those skilled in the art that such equivalent constructionsdo not depart from the spirit and scope of the invention as set forth inthe appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawing, in which:

FIG. 1 illustrates a wireless local area network (WLAN);

FIG. 2 illustrates a current carrier aggregation in WLAN;

FIG. 3 illustrates an impact of legacy stations on basic service set(BSS) throughput using current carrier aggregation in WLAN;

FIG. 4 illustrates an embodiment of an improved carrier aggregationscheme for a WLAN;

FIG. 5 illustrates another embodiment of a carrier aggregation schemefor a WLAN;

FIG. 6 illustrates another embodiment of a carrier aggregation schemefor a WLAN;

FIG. 7 illustrates an embodiment method for carrier aggregation forwireless networks;

FIG. 8 illustrates another embodiment method for carrier aggregation forwireless networks; and

FIG. 9 is a diagram of a processing system that can be used to implementvarious embodiments.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the embodiments andare not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

FIG. 1 shows a wireless local area network (WLAN) 100 comprising onemore stations (STAs) 110 and an access point (AP) 120 connected to aservice provider network 130. The STA 110 may be any of various devices,such as a cell phone, laptop, tablet, smart sensor, handheld or consumerelectronic device, and other user devices that have a Wi-Fi (or IEEE802.11) interface that can interact with a Wi-Fi network. These devicesalso may be able to interact with other types of communication networks,such as a cellular network. The AP 120 provides the connected STAs 110access to the service provider network 130 to provide various services(e.g., IP data services) to the STAs 110. The AP 120 and one or moreSTAs can form a basic service set (BSS), which is the basic buildingblock of an IEEE 802.11 WLAN. The AP 120 signals the BSS to the STAs110, which compete to use the BSS for transmission (e.g., each STA 110at a time). A BSS generally can be identified by a service setidentifier (SSID), which may be configured and broadcasted by the AP 120to the STAs 110.

Carrier aggregation is supported both in WLAN and cellular (LTE-A)standards. FIG. 2 shows a current carrier aggregation scheme 200 in acommon WLAN scenario where the available spectrum (unlicensed) isdivided into 20 mega Hz (MHz) channels. The concepts of primary (P) andsecondary (S) (also known as non-primary) channels are introduced inIEEE 802.11n to extend the channel bandwidth to 40 MHz. Each 40 MHzchannel consists of a primary 20 MHz and a secondary 20 MHz channels.Primary channels are implemented to ensure backward compatibility withlegacy devices, where the AP sends management and control frames overthe primary channel using legacy frame format. Concepts introduced inIEEE 802.11n were extended in IEEE 802.11ac to support wider channels upto 160 MHz. FIG. 2 shows a scenario where the wider channel isconstructed using contiguous 20 MHz channels. The use of non-contiguouschannels also is supported in IEEE 802.11ac.

FIG. 3 shows the impact of legacy stations on BSS throughput. Legacy-aand Legacy-n refer to a Legacy IEEE 802.11a station and a Legacy IEEE802.11n station, respectively. In the WLAN, the P and at least one S aredefined for the entire basic service set (BSS). The use of P and Schannels in WLAN limits the use of the available spectrum. The positionof the P channel and the position of the S channel relative to the Pchannel determine the operating channels of the AP and BSS. According tothis WLAN carrier aggregation paradigm, when the P channel is seized andused for transmission (e.g., by a STA), other channels in the same BSSthat remain available are not allowed for use by other transmissionssince the P channel, and therefore the entire BSS, is already accessedor used. Since the available channels cannot be used for othertransmissions, bandwidth resource and hence throughput is wasted. Forinstance, when Legacy-a gains access to the medium, it transmits itsframes using the primary channel. The rest of the 20 MHz channels withinthe BSS may be available but cannot be used because the primary channelis utilized for transmission by Legacy-a. Similarly, Legacy-n may useonly 40 MHz from the entire BSS, resulting in unused 20 MHz channels inthe BSS. Since the unused 20 MHz channels cannot be used for othertransmissions, bandwidth resource is wasted.

Embodiments are provided herein for improving carrier aggregation forWLANs and other networks that use similar carrier aggregation withprimary and secondary channels. For example, the embodiments may beimplemented in Wi-Fi networks and devices, such as Wi-Fi access points,Wi-Fi stations, and the like. The embodiments use multiple primarychannels or an alternate primary channel within the same BSS to allowdifferent transmissions the access to the BSS, as described below. Theembodiments also include inter-band carrier aggregation. Since moretransmissions can use the channels within the BSS, available(unlicensed) spectrum bandwidth resource can be conserved or used, whichimproves overall throughput of the network and allows more transmissions(e.g., by STAs) over limited resource.

FIG. 4 shows an embodiment of an improved carrier aggregation scheme400. To allow efficient utilization of the available spectrum, multipleprimary channels can be used within a BSS. With multiple primarychannels, different transmissions can cover all or a significant portionof the available spectrum. The network or AP may slice the spectrum intodifferent bandwidth aggregated channels using corresponding primarychannels. For instance, three primary 20 MHz channels are used in thisscenario. The first primary channel defines a 20 MHz channel (asecondary is not needed), and the second and the third primary channelsdefine 40 MHz and 80 MHz channels, respectively. The AP can directassociated stations to compete on the appropriate primary channel, givenstation bandwidth requirements. For example, legacy stations can use theavailable 20 MHz channel, while other stations that support morebandwidth can use the 40 MHz and 80 MHz channels. Each of the stationsseizes a corresponding portion of the BSS by allocating and using thecorresponding P channel. Multiple primary channels also can be used toidentify dedicated downlink (DL) and uplink (UL) channels of the same ordifferent bandwidth. For example, within the BSS, the first and secondprimary channels (of 20 and 40 MHz respectively) can be allocated for ULtransmissions, while the third primary channel can be used for DLtransmission. The secondary channels are also used for UL and DLtransmissions as their corresponding P channels. The scheme 400effectively segments the BSS into separate bandwidth segments to servemore than one transmission. In an embodiment, each segment bandwidthdefined by a corresponding P channel in the BSS can be assigned acorresponding BSS ID.

FIG. 5 shows an embodiment of another carrier aggregation scheme 500. Toallow efficient utilization of the available spectrum, at least onealternate primary (P′) channel can be used within the BSS in addition tothe P channel. For example, a 160 MHz BSS is established where at leastone alternate primary (P′) channel is defined to divide the BSSbandwidth into at least two channels. In the scenario of FIG. 5, thefirst 80 MHz channel portion is defined by the P channel, and the second80 MHz portion is defined by a P′ channel. However, more P′ channels canbe included to define more than two portions. When the primary channelis busy, e.g., serving a legacy station, the remaining BSS portions (asdefined by the P′ channels) can be used to serve other stations. Thebandwidth defined by the P′ channels can be used by other stations ifthey are available and not used by the station using the P channel.Frames transmitted using the P channel or P′ channels can be indicatedby a field in the PHY or a Media Access Control (MAC) header of thetransmitted frames.

FIG. 6 illustrates an embodiment of another carrier aggregation scheme600. In this scheme, carrier aggregation is extended to includeinter-band carrier aggregation. Specifically, the BSS is extendedbetween multiple bands (or non-contiguous portions of spectrumbandwidth). For example, the BSS is extended between two bands in thescenario of FIG. 6. Each band has its own primary and secondarychannels, which can be used for backward compatibility and/orcoexistence. The different bands can also be defined using primary andalternate primary channels, e.g., similar to the scheme 500.Additionally, each band of the BSS, can be further segmented intomultiple portions that can be used by different transmissions. Theindividual bands of the BSS can be further segmented using multiple Pchannels as in the scheme 400, or using P and P′ channels as in thescheme 500.

FIG. 7 shows an embodiment method 700 for carrier aggregation forwireless networks, which may correspond to any of the embodiment schemes400, 500, and 600 above. The method 700 may be implemented by a networkcomponent, such as the AP or a network controller. At step 710, aplurality of bandwidth channels are selected for a BSS. The channels maybe of the same bandwidth, for example of 20 MHz, or different bandwidth.Further, the channels may be contiguous or non-contiguous (e.g.,separate bands of the spectrum). At step 720, the BSS is segmented intomultiple segments using multiple primary channels, or a primary channelwith at least one alternate primary channel, to define each segment. Inadditional to a P or P′ channel, one or more S channels may be includedin any segment. The P or P′ channels may also be located innon-contiguous bands that form the BSS. At step 730, the locations ofthe P, P′, and S channels for each segment are broadcasted in thenetwork, e.g., to any listening STAs and/or APs. At step 740, the method700 listens to a transmission on any of the defined segments at thelocations of the P or P′ channels.

FIG. 8 shows an embodiment method 800 for carrier aggregation forwireless networks, which may correspond to any of the embodiment schemes400, 500, and 600 above. The method 800 may be implemented by a STA oran AP to determine channel bandwidth for transmission. At step 810, BSSinformation is received, indicating the primary, alternate primary ifincluded, and secondary channels in a BSS. At step 820, upon determiningto start a transmission (or detection), the STA or AP checks for a freeor unused segment in the BSS for transmission, e.g., on UL or DL. Forinstance, the STA or AP checks for a free P channel. Alternatively, if aP channel is used, the STA or AP checks for a free P′ channel. At step830, upon detecting a free P or P′ channel, frames are transmitted (ordetected/received) using the bandwidth channel defined for the P or P′channel. The channel may be an aggregation of multiple channelsincluding secondary channels. The channel may also be located in one ormore non-contiguous bands for the BSS. In a scenario, the STA or AP maycheck for a free channel (e.g., free P or P′ channel) that is dedicatedfor UL or DL transmission.

FIG. 9 is a block diagram of an exemplary processing system 900 that canbe used to implement various embodiments. Specific devices may utilizeall of the components shown, or only a subset of the components andlevels of integration may vary from device to device. For example, thedevices include the APs and the STAs of a WLAN or a Wi-Fi system.Furthermore, a device may contain multiple instances of a component,such as multiple processing units, processors, memories, transmitters,receivers, etc. The processing system 900 may comprise a processing unit901 equipped with one or more input devices, such as a microphone,mouse, touchscreen, keypad, keyboard, and the like. Also, processingsystem 900 may be equipped with one or more output devices, such as aspeaker, a printer, a display, and the like. The processing unit mayinclude central processing unit (CPU) 910, memory 920, mass storagedevice 930, video adapter 940, and I/O interface 990 connected to a bus995.

The bus 995 may be one or more of any type of several bus architecturesincluding a memory bus or memory controller, a peripheral bus, videobus, or the like. The CPU 910 may comprise any type of electronic dataprocessor. The memory 920 may comprise any type of system memory such asstatic random access memory (SRAM), dynamic random access memory (DRAM),synchronous DRAM (SDRAM), read-only memory (ROM), a combination thereof,or the like. In an embodiment, the memory 920 may include ROM for use atboot-up, and DRAM for program and data storage for use while executingprograms. The mass storage device 930 may comprise any type of storagedevice configured to store data, programs, and other information and tomake the data, programs, and other information accessible via the bus995. The mass storage device 930 may comprise, for example, one or moreof a solid state drive, hard disk drive, a magnetic disk drive, anoptical disk drive, or the like.

The video adaptor 940 and I/O interface 990 provide interfaces to coupleexternal input and output devices to the processing unit. Asillustrated, examples of input and output devices include the display960 coupled to the video adapter 940 and the mouse/keyboard/printer 970coupled to the I/O interface 990. Other devices may be coupled to theprocessing unit 901, and additional or fewer interface cards may beutilized. For example, a serial interface card (not shown) may be usedto provide a serial interface for a printer.

The processing unit 901 also includes one or more network interfaces950, which may comprise wired links, such as an Ethernet cable or thelike, and/or wireless links to access nodes or different networks. Thenetwork interface 950 allows the processing unit 901 to communicate withremote units via one or more networks 980. For example, the networkinterface 950 may provide wireless communication via one or moretransmitters/transmit antennas and one or more receivers/receiveantennas. In an embodiment, the processing unit 901 is coupled to alocal-area network or a wide-area network for data processing andcommunications with remote devices, such as other processing units, theInternet, remote storage facilities, or the like.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods might beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

In addition, techniques, systems, subsystems, and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A method comprising: transmitting, by a wirelessdevice, a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit(PPDU), wherein a channel indicator in a media access control (MAC)header of the PPDU indicates whether the PPDU is transmitted over aprimary channel.
 2. The method of claim 1, wherein the channel indicatorin the MAC header of the PPDU indicates that the PPDU is transmittedover a primary channel.
 3. The method of claim 1, wherein the channelindicator in the MAC header of the PPDU directly indicates that the PPDUis transmitted over an alternate primary channel.
 4. The method of claim1, wherein the wireless device is an access point (AP).
 5. The method ofclaim 1, wherein the wireless device is a mobile device.
 6. A wirelessdevice comprising: a processor; and a non-transitory computer readablestorage medium storing programming for execution by the processor, theprogramming including instructions to: transmit a Physical LayerConvergence Protocol (PLCP) Protocol Data Unit (PPDU), wherein a channelindicator in a media access control (MAC) header of the PPDU indicateswhether the PPDU is transmitted over a primary channel.
 7. The wirelessdevice of claim 6, wherein the channel indicator in the MAC header ofthe PPDU indicates that the PPDU is transmitted over a primary channel.8. The wireless device of claim 6, wherein the channel indicator in theMAC header of the PPDU directly indicates that the PPDU is transmittedover an alternate primary channel.
 9. A method comprising: receiving, bya wireless device, a Physical Layer Convergence Protocol (PLCP) ProtocolData Unit (PPDU); and determining whether the PPDU was received over aprimary channel based on a channel indicator in a media access control(MAC) header of the PPDU.
 10. The method of claim 9, wherein the channelindicator in the MAC header of the PPDU indicates that the PPDU istransmitted over a primary channel.
 11. The method of claim 9, whereinthe channel indicator in the MAC header of the PPDU directly indicatesthat the PPDU is transmitted over an alternate primary channel.
 12. Themethod of claim 9, wherein the wireless device is an access point (AP).13. The method of claim 9, wherein the wireless device is a mobiledevice.
 14. A wireless device comprising: a processor; and anon-transitory computer readable storage medium storing programming forexecution by the processor, the programming including instructions to:receive a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit(PPDU); and determine whether the PPDU was received over a primarychannel based on a channel indicator in a media access control (MAC)header of the PPDU.
 15. The wireless device of claim 14, wherein thechannel indicator in the MAC header of the PPDU indicates that the PPDUis transmitted over a primary channel.
 16. The wireless device of claim14, wherein the channel indicator in the MAC header of the PPDU directlyindicates that the PPDU is transmitted over an alternate primarychannel.
 17. A method by a network component for carrier aggregation forwireless networks, the method comprising: transmitting, by a wirelessdevice, a Physical Layer Convergence Protocol (PLCP) Protocol Data Unit(PPDU), wherein a bandwidth indicator in a media access control (MAC)header of the PPDU indicates an amount of bandwidth occupied by thePPDU.
 18. The method of claim 17, wherein the wireless device is anaccess point (AP).
 19. The method of claim 9, wherein the wirelessdevice is a mobile device.
 20. The wireless device of claim 14, whereinthe wireless device is an access point (AP).
 21. The wireless device ofclaim 14, wherein the wireless device is a mobile device.